M377

The M377 is a Tek-made amplifier integrated circuit designed by John Addis. It is used in the 11A16, 11A32, 11A33, 11A34, and 11A52.

About the M377, John Addis says:

The M377 was a single channel plugin on a chip with 0 V common mode input and output voltages, excellent variable gain control, two four pole bandwidth limits, three outputs which could be separately inverted and turned on or off.

It was the first wideband analog IC with level shift on chip (allowing 0 V common mode input and output and without PNP transistors), first wideband amplifier with any on-chip bandwidth limit selection, first to have more than two fixed gain settings (it has six), and first to require only one transient response adjustment (no thermals), and the first to have a highly linear relationship between a control voltage and gain. It also had excellent overdrive recovery.

The packaged M377 die has the following Tek part numbers:

• 165-2129-03
• 165-2089-06
• 155-2089-05 (11A33)

The M377 has one input (differential) and three differential outputs which are identical circuits. Each output has a its own control pins for:

• Output invert
• Output enable
• High-frequency adjustment. The HF ADJ pins have 2k ohms input resistance to ground. The nominally acceptable inputs are ±1V to ground. Because the input resistance tracks the nichrome standard resistors inside the chip, the input is actually current sensitive, not that it makes much difference. This current affects the standing current in a feedback amplifier and hence its open loop gain. At low frequencies, the gain of the M377 is determined entirely by resistor values. At high frequencies, there is phase shift and changing the open loop gain will also change the closed loop gain, hence the transient response.

This means that the gain of the closed loop and hence the hf gain of the amplifier varies with the current in the HF ADJ input.

Instrument	Instrument SN range	Part Number	Output R/side	Components on ceramic hybrid
11A32	B010100 - B031028	165-2089-03	100 ohms	M377 chip only
11A32	B031029 - up	165-2089-05	100 ohms	M377 chip only
11A34	B010100 - B031044	165-2089-04	200 ohms	M377 chip only
11A34	B031045 - up	165-2089-06	200 ohms	M377 chip only
11A52	B010100 - B010179	165-2129-02	100 ohms	Diode bridge + 50 ohm input R + M377 chip
11A52	B010180 - up	165-2129-03	100 ohms	Diode bridge + 50 ohm input R + M377 chip

165-2089-xx Pinout

In the 11A32, DISPLAY output 3, TRIGGER is output 2, and AUX SIG is output 1.

Pin	Function	Notes
1	GP0	gain select bit 0
2	STB	data strobe for gain and bandwidth limit
3	+15V
4	+Vin
5	Analog ground
6	-Vin
7	Analog ground
8	Var Gain
9	-5V
10	-5V
11	Output 1 Invert
12	Output 1 Enable
13	Analog Ground
14	+5V
15	Output 2 Invert
16	Output 2 Enable
17	Output 3 Invert
18	Output 3 Enable
19	-Output 3
20	+Output 3
21	Output 3 HF Adjust
22	-Output 2
23	+Output 2
24	Output 2 HF Adjust
25	-Output 1
26	+Output 1
27	Output 1 HF Adjust
28	Ground
29	Ground
30	Ground
31	+5V
32	-5V
33	BP1	bandpass select bit 1
34	BP0	bandpass select bit 0
35	GP2	gain select bit 2
36	GP1	gain select bit 1

Pin function legend

Power pins

Ground pins

HF signals

TTL digital control signals

analog control signals

• 

  M377 in an 11A52, as U310 and U410. Each M377 chip has a differential output impedance of 200 Ω. The two chips' outputs are in parallel, driving the output pins of the plug-in with a differential impedance of 100 Ω, or 50 Ω per side.

• 

  Two M377 chips (packaged as part number 165-2129-03) in an 11A52.

• 

  M377 die

• 
• 

  M377 Die pad names and numbers

Links

• Article in Electronic Engineering Magazine on M377 by John Addis